Assessment of UV-C/peroxymonosulfate process for the degradation of parabens mixture: Efficiency under different conditions, transformation pathways and ecotoxicity evolution

The extensive use of parabens in various products in combination with the low removal when treated with conventional methods have resulted in their widespread environmental occurrence. Ethyl-paraben (EtP), methylparaben (MeP) and propylparaben (PrP) are characteristic compounds of this category. Over the last years, Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) have shown promising results for the removal of organic micropollutants. As parabens commonly coexist in mixtures in aquatic systems, this study investigates the efficiency of UV-C/PMS process to remove EtP, MeP and PrP as a mixture in ultrapure water (UPW) and wastewater (WW). UV-C/PMS process was found to be efficient and high removal percentages were observed for all the parabens. However, the removal was dependent on the complexity of the water matrix. Different ions, as well as the dissolved organic matter that exist in wastewater can significantly influence the degradation of the mixture of parabens in UV-C/PMS system. The transformation was found to proceed through hydroxylation, dealkylation, radical coupling and cleavage of the aromatic rings. Although the toxicity was increased at the first stages in both UPW and WW, almost complete detoxification was achieved after prolonged time accompanied by the degradation of all the generated TPs. UV-C/PMS was also found being able to significantly reduce the toxicity from the wastewater.